Physics-Resistance & Resistivity
NEET Physics Resistance & Resistivity MCQ Question
Type: MCQ-numerical-Hard-Class 12
A copper wire has a resistivity of 1.7 × 10^-8 Ωm and is used to make a coil of resistance 8 Ω. If the wire has a length of 20 m, what is the cross-sectional area of the wire?
A
25 × 10^-7 m²
B
5.25 × 10^-7 m²
C
6.25 × 10^-7 m²
D
7.25 × 10^-7 m²
Correct Answer
Option A
Detailed Explanation
Using the formula R = ρ(L/A), where R is resistance, ρ is resistivity, L is length, and A is cross-sectional area, we can solve for A: A = ρL/R = (1.7 × 10^-8 Ωm)(20 m) / 8 Ω = 4.25 × 10^-7 m².
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